pandaproxy: Improve header validation

[BenPope]

Cover letter

Ensure consistency between request validation and Swagger UI command generation

• Requests without a body do not require Content-Type validation
• Swagger: Remove consumes for empty body requests
• Swagger: Ensure produces for all endpoints to prevent SwaggerUI generating application/json

Swagger documented on SwaggerHub

Signed-off-by: Ben Pope ben@vectorized.io

Release notes

Improvements

• Pandaproxy REST: Improve header validation and Swagger API

[CLAassistant]

All committers have signed the CLA.

[NyaliaLui]

Looks like something is returning JSON as a valid content-type and breaking one of the tests.

[BenPope]

Looks like something is returning JSON as a valid content-type and breaking one of the tests.

The test was checking that the content type is specifically rejected. I see no need.

[dotnwat]

Requests without a body do not require Content-Type validation

Is it really about the empty body or is it more about GET vs {POST,PUT}?

[BenPope]

Requests without a body do not require Content-Type validation

Is it really about the empty body or is it more about GET vs {POST,PUT}?

There are GET requests in the API which do have a body.

I imagine it's possible that v1 had a different format to v2 or maybe v3 is different (although they pretty much dropped Accept and Content-Type for v3).

It may even be possible to change the query parameters based on the Content-Type, although that would make it tricky to build a Swagger description, and pretty much upset every user and implementer.